Flammable refrigerant systems and compressors

ABSTRACT

The systems and compressors for use with flammable refrigerants can include features that can reduce or address the generation of sparks or arcs internal or external to the compressor that could ignite the flammable refrigerant. The systems and compressors can also include features that can reduce or address leakage into or out of the hermetic compressor shell which could create a flammable atmosphere that could be ignited if the flammable atmosphere came into contact with an ignition source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/726,676, filed Nov. 15, 2012, entitled SYSTEMS AND COMPRESSORS USING FLAMMABLE REFRIGERANT, and U.S. Provisional Application No. 61/726,672, filed Nov. 15, 2012, entitled HERMETIC ELECTRICAL FEEDTHROUGH ASSEMBLY FOR A COMPRESSOR, both of which Applications are incorporated by reference herein in their entirety.

BACKGROUND

The application generally relates to systems and compressors using a flammable refrigerant.

When using flammable refrigerant in a compressor and vapor compression system, numerous matters have to be addressed for safety and other reasons. Some examples of the matters that have to be addressed include: 1) refrigerant leaks that are external to the compressor, which can result in a flammable state that is a fire or explosion hazard; 2) overcharge of refrigerant that could generate a flammable state if a leak occurred; 3) mechanical failure (possibly from thermal contributions) that could cause a refrigerant leak; and 4) spark or arc generation from any source (such as a loose connection), internal or external to the compressor, which can result in a fire or explosion hazard if a flammable state is present. The determination of a flammable state or atmosphere can be based on specific air (oxygen) and refrigerant (fuel) ratios in the space that contains the refrigerant.

FIG. 1 shows a top, partial cross-sectional view of a prior art compressor 100. The compressor 100 has a shell 110 that provides a hermetically sealed environment for electrical and mechanical components inside the shell 110. To maintain proper operation of the compressor 100, the integrity of the hermetically sealed environment cannot be breached. Further, when a flammable refrigerant is used in the compressor 100 as the working fluid, any sparking or arcing inside or outside the compressor 100 should be avoided.

One type of electrical connection into the hermetically sealed environment of the shell 110 can be provided by a power terminal 112. The power terminal 112 has to maintain the hermetically sealed environment while withstanding the harsh operating conditions associated with the compressor 100. The power terminal 112 can be located within an aperture in the shell 110. The power terminal 112 can have a cup-shaped metal collar 126 with a bottom wall. The bottom wall has holes that permit conductor pins 128 to pass through the power terminal 112 to provide the electrical connection through the shell 110. The collar 126 is sealed in the shell aperture by welding and the pins 128 are sealed within the collar 126 by fused glass insulation. To further stabilize the power terminal 112, the fused glass insulation surrounding the pins 128 can be covered with epoxy or shielded by ceramic collars.

A fence 130 can surround and protect the power terminal 112. A molded plug (not shown) can be configured to couple with the fence 130 and, thereby, make an electrical connection with the pins 128 outside the shell 110. To accomplish this connection on the outside of the shell, the pins 128 can be provided with a tab (not shown). For example, each pin 128 may include an attached, e.g., welded, 0.250 inch tab that can connect to a 0.250 inch spade connector crimped onto the end of a voltage supply wire or conductor. Plugs, tabs, connectors or wires similar to those used on the outer ends of the pins 128 can be used on the inner end of the pins 128 to accomplish the electrical connection between the electrical components inside the shell 110 and the power terminal 112. Any of the previously described connections, e.g., pin-tab, tab-connector, connector-wire, can become corroded or loose and result in arcing or sparking that is undesirable when using a flammable refrigerant due to the risk of fire or explosion inside (or outside) of the shell 110. Further, any of the seals associated with the components of the terminal 112 can deteriorate and provide a leakage path into or out of the shell 110.

Therefore, what is needed is one or more systems and/or methods to increase the safety and reliability of a compressor using a flammable refrigerant by reducing or addressing the risks of sparking or arcing internal or external to the compressor and by reducing or addressing the risks associated with leakage into or out of the hermetic compressor shell.

SUMMARY

The present application is directed to a compressor. The compressor includes a shell and a compression mechanism. The shell has an upper portion connected to a lower portion to form an enclosed space. The compression mechanism is positioned in the lower portion of the shell. The compressor also includes a motor connected to the compression mechanism by a shaft to power the compression mechanism. The motor includes a rotor connected to the shaft and a stator to rotate the rotor. The rotor is positioned in the enclosed space of the upper portion of the shell and the stator is positioned outside of the upper portion of the shell.

The present invention is also directed to a system. The system includes a compressor, a condenser and an evaporator connected in a circuit and circulating a flammable refrigerant. The system additionally includes a motor connected to the compressor to power the compressor. The motor includes a stator and a rotor. The compressor includes a compression mechanism and a shell. The shell has an upper portion connected to a lower portion. The compression mechanism is positioned in the lower portion of the shell. The upper portion of the shell includes a non-magnetic material. The rotor is positioned in the upper portion of the shell and the stator is positioned outside the upper portion of the shell. The stator transmits electromagnetic energy to the rotor.

One advantage of the present application is the reduction of sources for sparking or arcing near a flammable refrigerant.

Other features and advantages of the present invention will be apparent from the following, more detailed description of the embodiments, taken in conjunction with the accompanying drawings which show, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top, partial cross-sectional view of a prior art compressor.

FIGS. 2 and 3 schematically show embodiments of vapor compression systems.

FIG. 4 shows an embodiment of a compressor using an embodiment of an electrical feedthrough assembly.

FIG. 5 shows an embodiment of a compressor using an embodiment of an external stator.

FIGS. 6 and 7 schematically show partial cross sections of embodiments of the connection between the upper portion and the lower portion of the compressor shell.

FIG. 8 schematically shows a partial side view of an embodiment of the upper portion of the compressor shell.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As shown in FIGS. 2 and 3, a vapor compression system 300 includes a compressor 302, a condenser 304, and an evaporator 306 (see FIG. 2) or a compressor 302, a reversing valve 350, an indoor unit 354 and an outdoor unit 352 (see FIG. 3). The vapor compression system can be included in a heating, ventilation and air conditioning (HVAC) system, refrigeration system, chilled liquid system or other suitable type of system. Some examples of refrigerants that may be used in vapor compression system 300 are: hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407C, R-404A, R-134a and R-32 (a component of R410A and R407C); hydrofluoro olefin (HFO) refrigerants, also known as “unsaturated HFCs,” such as R1234yf; inorganic refrigerants like ammonia (NH3), R-717 and carbon dioxide (CO2), R-744; hydrocarbon (HC) based refrigerants such as propane (R-290), isobutane (R-600a) or propene (R-1270), or any other suitable type of refrigerant. The hydrocarbon based refrigerants may be referred to as “flammable” refrigerants and can have an ASHRAE flammability class of 3. Other types of “flammable” refrigerants can include R-32, ammonia (R-717) and HFO refrigerants, each of which can have an ASHRAE flammability class of 2L. In another embodiment, flammable refrigerant can include any refrigerant classified in ASHRAE flammability class of 3 or ASHRAE flammability class of 2L.

The vapor compression system 300 can be operated as an air conditioning system, where the evaporator 306 is located inside a structure or indoors, i.e., the evaporator is part of indoor unit 354, to provide cooling to the air in the structure and the condenser 304 is located outside a structure or outdoors, i.e., the condenser is part of outdoor unit 352, to discharge heat to the outdoor air. The vapor compression system 300 can also be operated as a heat pump system, i.e., a system that can provide both heating and cooling to the air in the structure, with the inclusion of the reversing valve 350 to control and direct the flow of refrigerant from the compressor 302. When the heat pump system is operated in an air conditioning mode, the reversing valve 350 is controlled to provide for refrigerant flow as described above for an air conditioning system. However, when the heat pump system is operated in a heating mode, the reversing valve 350 is controlled to provide for the flow of refrigerant in the opposite direction from the air conditioning mode. When operating in the heating mode, the condenser 304 is located inside a structure or indoors, i.e., the condenser is part of indoor unit 354, to provide heating to the air in the structure and the evaporator 306 is located outside a structure or outdoors, i.e., the evaporator is part of outdoor unit 352, to absorb heat from the outdoor air.

Referring back to the operation of the system 300, whether operated as a heat pump or as an air conditioner, the compressor 302 is driven by the motor 106 that is powered by motor drive 104. The motor drive 104 receives AC power having a particular fixed line voltage and fixed line frequency from AC power source 102 and provides power to the motor 106 at a preselected voltage and preselected frequency. In another embodiment, the motor 106 can be powered directly from the AC power source 102. The motor 106 used in the system 300 can be any suitable type of motor that can be powered by a motor drive 104. The motor 106 can be any suitable type of motor including, but not limited to, an induction motor, a switched reluctance (SR) motor, or an electronically commutated permanent magnet motor (ECM). In another embodiment, the motor 106 can be a DC motor that would connect to a DC power source instead of AC power source 102.

Referring back to FIGS. 2 and 3, the compressor 302 compresses a refrigerant vapor and delivers the vapor to the condenser 304 through a discharge line (and the reversing valve 350 if configured as a heat pump). The compressor 302 can be suitable type of hermetic or semi-hermetic compressor including, but not limited to, a reciprocating compressor, rotary compressor, screw compressor, swag link compressor, scroll compressor, spool compressor, centrifugal compressor, or turbine compressor. The refrigerant vapor delivered by the compressor 302 to the condenser 304 enters into a heat exchange relationship with a fluid, e.g., air or water, and undergoes a phase change to a refrigerant liquid as a result of the heat exchange relationship with the fluid. The condensed liquid refrigerant from the condenser 304 flows through an expansion device to the evaporator 306.

The condensed liquid refrigerant delivered to the evaporator 306 enters into a heat exchange relationship with a fluid, e.g., air or water, and undergoes a phase change to a refrigerant vapor as a result of the heat exchange relationship with the fluid. The vapor refrigerant in the evaporator 306 exits the evaporator 306 and returns to the compressor 302 by a suction line to complete the cycle (and the reversing valve arrangement 350 if configured as a heat pump). In other exemplary embodiments, any suitable configuration of the condenser 304 and the evaporator 306 can be used in the system 300, provided that the appropriate phase change of the refrigerant in the condenser 304 and evaporator 306 is obtained. For example, if air is used as the fluid to exchange heat with the refrigerant in the condenser or the evaporator, then one or more fans can be used to provide the necessary airflow through the condenser or evaporator. The motors for the one or more fans may be powered directly from the AC power source 102 or a motor drive, including motor drive 104.

FIG. 4 shows an embodiment of a hermetic compressor. Compressor 2 may be connected to a refrigeration or heating, ventilation and air conditioning (HVAC) system 300. The compressor 2 is shown as a reciprocating compressor, but compressor 2 can be any suitable type of hermetic compressor as previously described. The compressor 2 can be connected to evaporator 306 by a suction line that enters the suction port 14 of compressor 2. The suction port 14 can be in fluid communication with a suction plenum 12. Refrigerant gas from the evaporator 306 enters the compressor 2 through the suction port 14 and then flows to the suction plenum 12 before being compressed. In one embodiment, the refrigerant gas from the suction port 14 can fill the interior space of the compressor housing before flowing to the suction plenum 12.

The compressor 2 can use an electrical motor 18. As shown in FIG. 4, motor 18 is an induction motor having a stator 21 and a rotor 23, however any other suitable type of electrical motor may be used. A shaft assembly 25 extends through the rotor 23. The bottom end 29 of the shaft assembly 25 extends into an oil sump 405 and includes a series of apertures 27. Connected to the shaft assembly 25 below the motor is a compression device. As shown in FIG. 4, the compression device can be a piston assembly 31 that has two pistons. A connecting rod 33 is connected to a piston head 34, which moves back and forth within a cylinder 36. The cylinder 36 includes a gas inlet port 38 and a gas discharge port 41. Associated with ports 38, 41 are suction valves and discharge valves. The gas inlet port 38 is connected to an intake tube 55, which is in fluid communication with the suction plenum 12.

The motor 18 can be activated by a signal in response to the satisfaction of a predetermined condition, for example, an electrical signal from a thermostat when a preset temperature threshold is reached. While a thermostat is used as an example, it should be known that any type of device or signal may be used to activate the compressor. When the compressor is activated, electricity is supplied to the stator 21, and the windings in the stator 21 cause the rotor 23 to rotate. Rotation of the rotor 23 causes the shaft assembly 25 to turn. When the shaft assembly 25 is turning, oil sump fluid in the oil sump 405 enters the apertures 27 in the bottom end 29 of the shaft and then moves upward through and along the shaft 25 to lubricate the moving parts of the compressor 2.

Rotation of the rotor 23 also causes reciprocating motion of the piston assembly 31. As the assembly 31 moves to an intake position, the piston head 34 moves away from gas inlet port 38, the suction valve opens and refrigerant fluid is introduced into an expanding cylinder 36 volume. The gas is pulled from the suction plenum 12 through the intake tube 55 to the gas inlet port 38 where the gas passes through the suction valve and is introduced into the cylinder 36. When the piston assembly 31 reaches a first end (or top) of its stroke, shown by movement of the piston head 34 to the right side of the cylinder 36 of FIG. 4, the suction valve closes. The piston head 34 then compresses the refrigerant gas by reducing the cylinder 36 volume. When the piston assembly 31 moves to a second end (or bottom) of its stroke, shown by movement of piston head 34 to the left side of cylinder 36 of FIG. 4, a discharge valve is opened and the compressed refrigerant gas is expelled through the gas discharge port 41. The compressed refrigerant gas flows from the gas discharge port 41 into a muffler 51 then through an exhaust or discharge tube 53 to exit the compressor 2 into a conduit connected to a condenser.

The motor 18 can be positioned within the top portion of the compressor 2, and the piston assembly 31 can be positioned below the motor 18. The oil sump 405 can be located at the bottom portion of the compressor 2. In one embodiment, a portion of the piston assembly 31 can be submerged below the oil level in the oil sump 405. When the compressor is not operating, some of the refrigerant in compressor 2 may condense and fall by force of gravity into the oil sump 405 and mix with the oil in the oil sump 405 or be absorbed into the oil in the oil sump. The oil in the oil sump 405 is used to lubricate the mechanical portions of the compressor 2, such as shaft assembly 25. When liquid refrigerant mixes with the oil, the resulting liquid is a less effective lubricant. To avoid this problem, the oil sump fluid is heated with a heater 131 and the refrigerant is evaporated from the oil, leaving oil in the oil sump 405 to lubricate the components. The heater 131 can be positioned within the oil sump and mounted or secured to any suitable structure inside the compressor such as the piston assembly 31 or an interior surface of a compressor shell 39.

Power can be provided to the motor 18 and the heater 131, or any other electrical component inside the compressor shell 39, by use of an electrical feedthrough assembly 10. As shown in FIG. 4, the electrical feedthrough assembly 10 can be positioned in the top cylindrical portion of the compressor 2. However, in other embodiments, the electrical feedthrough assembly 10 can be positioned at any suitable location in the compressor shell 39.

The feedthrough assembly 10 can be used to provide power, control and/or communication signals to the compressor motor 18 and the heater 131. The feedthrough assembly 10 can eliminate all inside and outside terminal connections at the compressor shell 39 for the motor 18 and heater 131 by permitting the corresponding power and control conductors or wires to pass through the compressor shell 39 without interruption, i.e., a continuous conductor or wire is used.

FIG. 5 shows an embodiment of a hybrid semi-hermetic compressor, i.e., the rotor for the motor is inside the shell and the stator and overload protection (OLP) for the motor, along with corresponding electrical connections to a power source, are outside the shell. The hybrid semi-hermetic compressor can be considered a hermetic compressor because the shell for the compressor does not require any seals and can maintain a hermetic environment. Compressor 500 may be connected to a refrigeration or HVAC system 300. The compressor 500 can have a compression mechanism 502 positioned inside a shell or housing 400 that receives refrigerant gas from a suction inlet 504 that passes or travels through the shell 400. The compression mechanism 502 then provides compressed refrigerant gas to a discharge outlet 506 that travels or passes through the shell 400. The compression mechanism 502 can incorporate a compression mechanism from any of the previously described types of compressors, e.g., a reciprocating compressor, a rotary compressor, a screw compressor, a swag link compressor, a scroll compressor, a spool compressor, a centrifugal compressor, or a turbine compressor. The suction inlet 504 can be connected to the evaporator 306 of the HVAC system 300 and the discharge outlet 506 can be connected to the condenser 304 of the HVAC system 300.

The suction line 504 of compressor 500 is shown in FIG. 5 as directly flowing into the compression mechanism 502. However, in other embodiments, the suction line 504 can be in fluid communication with a suction plenum that can supply the compression mechanism 502. The suction plenum can be incorporated into the compression mechanism 502 and/or can be in communication with or incorporate all or part of the internal volume of the compressor 500. In one embodiment, the compressor 500 can include one or more filters, mufflers or other components between the suction inlet 504 and the compression mechanism 502. In another embodiment, the filters, mufflers or other components can be located upstream from the suction inlet 504 outside of the compressor 500. The discharge outlet 506 is shown in FIG. 5 as directly flowing from the compression mechanism 502. However, in other embodiments, the compressor 500 can include one or more mufflers, oil separators or other components between the compression mechanism 502 and the discharge outlet 506 or downstream from the discharge outlet.

The compressor 500 can use an electrical motor 510. As shown in FIG. 5, a stator 512 for the motor 510 can be positioned outside of the shell 400 and the rotor 514 for the motor 510 can be positioned within the shell 400. The motor 510 can be any suitable type of electrical motor that has a stator 512 and a rotor 514, including, but not limited to, an induction motor, an SR motor, an ECM or a DC motor. The rotor 514 can be connected to a shaft 516 that is used to drive the compression mechanism 502. In one embodiment, the bottom end of the shaft 516 can extend into an oil sump located in the bottom of the shell 400 to draw lubrication oil for the shaft 516 and compression mechanism 502.

The motor 510 can be activated by a signal in response to the satisfaction of a predetermined condition, for example, an electrical signal from a thermostat when a preset temperature threshold is reached. While a thermostat is used as an example, it should be known that any type of device or signal may be used to activate the motor 510 and compressor 500. When the compressor 500 and motor 510 are activated, electricity is supplied to the stator 512, and the windings in the stator 512 cause the rotor 514 to rotate. Rotation of the rotor 514 causes the shaft 516 to turn and move or rotate the compression mechanism 502.

Since the stator 512 for the motor 510 is located outside of the shell 400, the stator 512 can be wired to the corresponding power supply for the compressor 500 using any suitable wiring technique without the risk of introducing a spark or arc inside of the compressor shell 400. The stator 512 and rotor 514 can be positioned in close proximity to one another to permit the efficient transfer of electromagnetic energy between the stator 512 and rotor 514, i.e., to enable the stator 512 to turn or rotate the rotor 514.

The shell 400 can have a first or lower portion 402 that can include the compression mechanism 502 and a second or upper portion 404 that can include the rotor 514. The upper portion 404 can also include one or more bearings 408 positioned in a gap or space 409 between the top of the rotor 514 and upper portion 404 to prevent the shaft 516 and/or rotor 514 from touching or contacting the top and/or the sides of the upper portion 404. A gap or space 407 can separate the sides of the rotor 514 and an inner surface of the upper portion 404. In one embodiment, the gap or space 409 can be in the range of 0.250 to 0.750 inches and the gap or space 407 can be in the range of 0.005 to 0.030 inches. In another embodiment, the upper portion 404 can include one or more bearings positioned in the gap or space 407 between the rotor 514 and upper portion 404 to prevent the rotor 514 from touching or contacting the sides of the upper portion 404. The upper portion 404 and lower portion 402 can each have a closed end and an open end opposite the closed end with an opening that is circular, elliptical, oval or any other suitable geometric shape. The open end of the upper portion 404 can have a smaller diameter, circumference and/or perimeter than the open end of the lower portion 402.

In one embodiment, the outer surface of the upper portion 404 and/or the stator 512 can include guides or other suitable mechanisms, such as tabs and/or depressions, to ensure the proper alignment of the stator 512 relative to the upper portion 404 and rotor 514. In another embodiment, the inner surface of the upper portion 404 and/or the rotor 514 can include guides or other suitable mechanisms, such as tabs and/or depressions, to ensure the proper alignment and spacing of the rotor 514 relative to the inner surface of the upper portion 404. Depending on the configuration of the guides or other mechanisms used for positioning the stator 512 and rotor 514 relative to the upper portion 404, the guides or mechanism can either remain in place or be removed either through manual operation or operation of the motor 510. In a further embodiment, precision machining of one or more of the stator 512, the rotor 514 and the upper portion 404 can be performed to provide for the proper alignment of the stator 512 and the rotor 514.

In another embodiment as shown in FIG. 5, the rotor 514 can have a greater length than the corresponding stator portion, e.g., the stator teeth or projections, to ensure that the rotor 514 and stator 512 are in proper alignment when the stator 512 is mounted outside the upper portion 404. The rotor 514 can extend past either or both of the upper end and the lower end of the stator 512. In an alternate embodiment, the rotor 514 can have the same length as the corresponding stator portion.

A flange or ring portion 410 can be used to connect the upper portion 404 to the lower portion 402. The upper portion 404 can be hermetically connected to an inner portion of the flange portion 410 and the lower portion 402 can be hermetically connected to an outer portion of the flange portion 410 to provide a hermetically sealed environment within the compressor shell 400. In one embodiment, the flange portion 410 can be integral and/or continuous with the upper portion 404, i.e., no joint between the flange portion 410 and the upper portion 404, while in another embodiment, the flange portion 410 can be integral and/or continuous with the lower portion 402, i.e., no joint between the flange portion 410 and the lower portion 402. The flange portion 410 is shown in FIG. 5 with a generally linear cross-sectional shape extending substantially horizontally between the inner portion and the outer portion of the flange portion 410. As shown in FIGS. 6 and 7, the flange portion 410 could extend at an angle such that the inner portion of the flange portion 410 is at a different elevation than the outer portion of the flange portion 410. In other embodiments, the flange portion 410 can have other cross sectional shapes besides generally linear, including arch shapes, inverted arch shapes (e.g., horseshoe shape) or other suitable types of shapes and can extend either horizontally or at an angle. In still other embodiments, the cross-sectional shape of the flange portion 410 may be different in different locations to accommodate internal components or equipment in either the upper portion 404 or the lower portion 402.

To permit the stator 512 to transmit electromagnetic energy through the upper portion 404 to the rotor 514, the upper portion 404 can have a relatively thin material thickness. In one embodiment, the thickness for the upper portion can be between 0.02 and 0.1 inches. The material for the upper portion 404 can be any suitable material, including non-magnetic, non-conductive, paramagnetic and/or magnetic materials, that can permit the transfer of electromagnetic energy between the stator 512 and the rotor 514 In one embodiment, the upper portion 404 can be made from one or more of stainless steel (both austenitic and non-austenitic), polymer material(s), ceramic material(s), epoxy material(s), steel, sheet metal, or titanium. In contrast, the lower portion 402 and flange portion 410 can be made from conventional materials such as steel or sheet metal and can have a material thickness between 0.105 and 0.125 inches. However, in another embodiment, the flange portion 410 and/or the lower portion 402 can be made from the same material and/or have the same material thickness as the upper portion 404.

In one embodiment, the stator 512 can be press-fit onto the outer surface of the upper portion 404 to securely mount the stator 512 and to help minimize the distance between the stator 512 and the rotor 514. In another embodiment as shown in FIG. 8, the upper portion 404 can be made of a substantially non-magnetic and/or non-conductive material 802 with a plurality of magnetic portions 804 embedded or molded into the non-magnetic material 802 to insulate the magnetic portions 804. The positions of the magnetic portions 804 in the upper portion 404 can correspond to the location of corresponding teeth or projections from the stator 512 such that when the stator 512 is press-fit onto the upper portion 404 the teeth or projections from the stator 512 contact the magnetic portions 804 of the upper portion 404. The contact between the magnetic portions 804 of the upper portion 404 and the teeth or projections of the stator 512 can provide a direct path for the electromagnetic energy between the stator 512 and the rotor 514, i.e., the electromagnetic energy does not need to travel through the upper portion 404. In a further embodiment, the upper portion 404 can be made of a substantially magnetic material and only those areas of the upper portion 404 that correspond to the teeth or projections of the stator 512 can be surrounded by insulating or non-magnetic material. In still other embodiments, the stator 512 can be mounted using a suitable mounting technique.

In another embodiment, the stator 512 can be surrounded by an enclosure to provide protection to the stator 512. The enclosure for the stator 512 may or may not be hermetically sealed and may or may not be connected to the compressor shell 400.

In one embodiment, different types of compressor fittings, e.g., non-brazed connections, can be used with compressors 2 and 500. Some examples of suitable non-brazed compressor fittings can include Rotolock and high Q (high quality) compression fittings. A Rotolock fitting can be a special refrigeration fitting that uses a teflon ring seated against a machined surface enclosed by a threaded fitting.

In another embodiment, lubricant that minimizes the amount of refrigerant absorbed, which lowers the amount of refrigerant charge required, can be used with compressors 2 and 500. Compressors 2 or 500 may also include components that do not require lubricant. For example, compressors 2 or 500 may use magnetic or sealed bearings that do not require lubricant. In an additional embodiment, depending on the properties of the refrigerant used by the compressor, the refrigerant itself could be used to lubricate certain components of the compressor.

In a further embodiment, a low pressure cut-out switch can be used with compressors 2 or 500 to make sure no oxygen enters the compressors 2 or 500 such that a flammable atmosphere or state is created. If the stator is internal to the compressor as shown in FIG. 4, an internal line break pressure switch can be used as a low pressure cut-out to disconnect the power to the motor to prevent sparking or arcing near the possible flammable atmosphere.

In still another embodiment, improved testing procedures can be used to ensure that no leaks are present in the compressor for the avoidance of a flammable atmosphere. Additional testing for leaks can be conducted after the compressor leaves the factory to detect leaks caused by system tubing breaks.

In yet another embodiment, the internal free volume of the compressor can be reduced by adjusting the configuration of the shell or by the insertion of “filler” such as solid blocks to reduce the amount flammable refrigerant stored in the compressor and to avoid a flammable atmosphere if a leak should occur.

In one embodiment, an arc detect circuit breaker can be used to eliminate ignition sources and avoid spark generation. A specialized board can be used to detect arcs in the compressor. The specialized control board can include enhanced sensitivities or can identify certain characteristics that are associated with arcs in a flammable refrigerant atmosphere or state.

In another embodiment, the motor 510 can be a variable speed permanent magnet (PM) motor or a line start PM motor.

In a further embodiment, the entire motor can be located outside of the compressor shell and a shaft seal can be used to provide the hermetic environment for the compressor shell, i.e., a semi-hermetic compressor. The external motor can have its own housing which can be hermetically sealed. If the external motor is mounted in its own housing, a sensor can be placed in the motor's housing to detect leaks from the shaft seal. When a leak is detected by the sensor, a control can be put into place to shut down the motor and compressor due to the leak.

As would be appreciated by those of ordinary skill in the pertinent art, the functions of several elements of the present application may, in alternative embodiments, be carried out by fewer elements, or a single element. Similarly, in some embodiments, any functional element may perform fewer, or different, operations than those described with respect to the illustrated embodiment. Also, functional elements shown as distinct for purposes of illustration may be incorporated within other functional elements, separated in different hardware or distributed in various ways in a particular implementation. Further, relative size and location are merely somewhat schematic and it is understood that not only the same but many other embodiments could have varying depictions.

All relative descriptions herein such as above, below, left, right, up, and down are with reference to the Figures, and not meant in a limiting sense. Relative descriptions such as inner and inward are with reference to being a direction toward the interior of a compressor shell whereas outer and outward are a direction away from the compressor. The illustrated assemblies can be understood as providing exemplary features of varying detail of certain embodiments, and therefore, components, modules, elements, and/or aspects of the illustrations can be otherwise added to, combined, interconnected, sequenced, separated, interchanged, positioned, and/or rearranged without materially departing from the disclosed systems or methods. Additionally, the shapes and sizes of components are also exemplary and unless otherwise specified, can be altered without materially affecting or limiting the disclosed technology.

It is important to note that the construction and arrangement of the present application as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this application, those who review this application can readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described in the application. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims.

Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation. 

What is claimed is:
 1. A compressor comprising: a shell, the shell having an upper portion connected to a lower portion to form an enclosed space; a compression mechanism, the compression mechanism being positioned in the lower portion of the shell; and a motor connected to the compression mechanism by a shaft to power the compression mechanism, the motor comprising: a rotor connected to the shaft, the rotor being positioned in the upper portion of the shell; and a stator to rotate the rotor, the stator being positioned outside of the upper portion of the shell.
 2. The compressor of claim 1 wherein the stator is mounted on an outer surface of the upper portion of the shell.
 3. The compressor of claim 1 wherein the upper portion of the shell comprises a non-magnetic material.
 4. The compressor of claim 3 wherein the non-magnetic material comprises austenitic stainless steel, a polymer material, a ceramic material, or an epoxy material.
 5. The compressor of claim 1 wherein the upper portion of the shell has a first material thickness and the lower portion of the shell has second material thickness greater than the first material thickness.
 6. The compressor of claim 5 wherein the first material thickness is in the range of 0.02 inches to 0.1 inches.
 7. The compressor of claim 1 further comprising a flange portion to connect the upper portion of the shell and the lower portion of the shell.
 8. The compressor of claim 7 wherein the flange portion is integral and continuous with one of the upper portion of the shell or the lower portion of the shell.
 9. The compressor of claim 8 wherein the flange portion is positioned at an angle with respect to the lower portion of the shell and is transverse to the lower portion of the shell.
 10. The compressor of claim 1 further comprising at least one bearing positioned between the rotor and an inner surface of the upper portion of the housing.
 11. The compressor of claim 1 wherein the upper portion of the shell has a first circumference and the lower portion of the shell has second circumference greater than the first circumference.
 12. A system comprising: a compressor, a condenser and an evaporator connected in a circuit and circulating a flammable refrigerant; a motor connected to the compressor to power the compressor, the motor comprising a stator and a rotor; the compressor comprising a compression mechanism and a shell, the shell having an upper portion connected to a lower portion, the compression mechanism being positioned in the lower portion of the shell; the upper portion of the shell comprising a non-magnetic material; the rotor being positioned in the upper portion of the shell; and the stator being positioned outside the upper portion of the shell, the stator transmitting electromagnetic energy to the rotor.
 13. The system of claim 12 wherein the stator is mounted on and in contact with an outer surface of the upper portion of the shell.
 14. The system of claim 12 wherein the non-magnetic material comprises austenitic stainless steel, a polymer material, a ceramic material, or an epoxy material.
 15. The system of claim 12 wherein the upper portion of the shell has a first material thickness and the lower portion of the shell has second material thickness greater than the first material thickness.
 16. The system of claim 12 further comprising a flange portion to connect the upper portion of the shell and the lower portion of the shell.
 17. The system of claim 16 wherein the flange portion is integral and continuous with one of the upper portion of the shell or the lower portion of the shell.
 18. The system of claim 12 further comprising at least one bearing positioned between the rotor and an inner surface of the upper portion of the housing.
 19. The system of claim 12 wherein the upper portion of the shell comprises a plurality of magnetic portions, each magnetic portion of the plurality of magnetic portions being separated by the non-magnetic portion.
 20. The system of claim 12 further comprising a motor drive to operate the motor at variable speeds, the motor drive comprising an arc detect circuit breaker. 